>> From the Library of Congress, in Washington, DC.
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^M00:00:25 Good morning, I'm Michelle [inaudible], a reference and research specialist in the science technology and business division at the Library of Congress. I'd like to welcome you to today's program, on finding hot towers in hurricanes. In which we'll learn about the amazing technology, dramatic science, and the brilliant scientist who coined the term 'hot tower' fifty years ago. This program is the fourth in a series of programs in 2013, and is presented through a collaboration now in its seventh year between the library of science technology and business division, and the NASA-Goddard Space Flight Center. On October 22nd, in 2012, NASA's tropical rainfall measuring mission satellite, TRMM, was monitoring TD-18, the eighteenth tropical depression of the season, which had which had formed over the Southwestern Caribbean Sea. In the storm, they saw a hot towering thunderstorm, over nine miles high, near its center of circulation, hinting that it could become a tropical storm. NASA scientists Owen Kelly and John Stout of George Mason University and NASA's Goddard Space Flight Center found that a tropical cyclone with a hot tower around its center of circulation was twice as likely to intensify within the next six hours than a cyclone that lacked a tower. That's exactly what happened on October 22nd when TRMM spotted hot towers in TD-18. It became tropical storm Sandy, just six hours later. Increasing the accuracy of hurricane intensity forecasts saves both lives and property. Starting fifty years ago, scientists have pursued a line of inquiry that has tried to connect hurricane intensity change to the existence of tall storm cells, called hot towers,that occasionally form near the eyes of some hurricanes. During the past decades, NASA's TRMM satellite has been able to collect definitive statistics on the association of hot towers and hurricane intensification. For the past fifteen years, Owen Kelly has been part of the group at NASA Goddard Space Flight Center who processes the data from the TRMM satellite, and the soon to be launched global precipitation measurement satellite. Hurricane hot towers were the topic of his PhD. dissertation at George Mason University, and he has written several papers on the subject; he has also been interviewed about his hurricane research for a documentary that aired in 2007 on the National Geographical Channel. Please join me in welcoming Dr. Owen Kelley.
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[Applause]
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Dr. Owen Kelley: Hi, thank you for that introduction, and thank you for coming. The introduction, I didn't write it, I really like it, I could spend a lot of time talking about the points she brought up, and I have to clarify one, that a single hot tower isn't enough, you need a sequence of them if you're going to alter the state of a hurricane. We'll get to that. So, why talk about hurricanes? The obvious answer is that they're scary. They're dangerous. They threaten life and property, and forecasts can fail. And as a scientist, the way I can contribute, is by changing how we think about hurricanes and improving our conceptual understanding of them. I'm not a forecaster, I'm not going to make next year's forecast better, but scientists can do something to help. So, let's see if I can advance this, it doesn't seem to be advancing. It's thinking about it.
>> It's thinking.
>> Dr. Owen Kelley: If the screen saver comes- oh, good. Okay, we're good. Okay, so, slide number two. So I personally have never suffered a loss from a hurricane. Fortunately, because Hurricane Sandy last year and Hurricane Irene the year before went basically right over my parents' house. And that was very scary. And as the storm approached, my satellite flew over these storms and it seemed urgent to get every little bit of information. The satellite, I work with, the TRMM satellite, is not an operational weather satellite. It's an experimental satellite that NASA built in cooperation with the Japanese actually and so we do three dimensional CAT scans of hurricanes and so the challenge for this lecture, the challenge for scientists is to improve our understanding of hurricanes. My challenge in this lecture is to try to change how you think about hurricanes. Hurricanes are wind and rain but by the end of the lecture, I want you to be able to imagine hurricanes as 'engines,' and engines that change energy from one form to another. And that's a powerful way to think about hurricanes and we'll see if I can bring you through that journey. This could loosely be called a hot tower. You could be driving home from work, and you see this, and you know the beltway's going to be stopped because there's going to be heavy rain, and lightening, and maybe hail pelting your roof, you know, so as a scientist I look at that and I say, 'I don't know if that's a hot tower, because all you're seeing is the surface of the cloud. And clouds can float around even when there's no rain in them. So, what I would want to know is, how high are up-drafts lifting precipitation inside it? Because it's the raining region inside the tower that gives you a clue to the up-drafts, and the up-drafts give you a clue to the energy being released. Again, its energy transformations that it's all about. So if you happen to be sitting in the international space station, this is what you might see when there's a hot tower. The sort of bubbly region on the right is where the updrafts are; there's in-flow coming at the surface, there are up-drafts in these narrow regions, and then an anvil spreads at the top. When the air can't rise any higher, then it just spreads out horizontally. I call them the exhaust fumes of the hot towers. So now we're going to look for hot towers in hurricanes. I'm showing you this because hurricanes are very messy, and there's a lot going on. And hot towers can really form anywhere in a hurricane. If they form far out from the eye, they can actually rob the low-level in-flow of moisture, which weakens the hurricane, because the real transformations occur in the eye wall, which is donut shaped, and it's surrounding the eye. So, we're going to have a little pop quiz here. This is Hurricane Isabel. Obviously, the upper level cloud cover is already covering the Northeastern United States: the eye wall is a day away from hitting Maryland, in 2003, so can you find the eye wall in this picture? First, you look for the dark eye, so I'm going to help you, that's the eye wall. Now the harder thing to see is that there's actually what looks like a hot tower forming on the edge of the eye wall. It's that circular region, it's rising up, as it matures, it'll send outflow in every direction, obscuring the eye, sometimes. And that's what we're going to study in this lecture. We're going to look at the eye wall of hurricanes, and look for hot towers there. So this is what we've got; we've got a definition, and we know they can form in hurricanes. So how do we find these things? So, I really like this picture. This is how they used to find hot towers. With a ruler and with print-outs. This is Dr. Joann Simpson in the 1950's; I'm using the term loosely. To me she's the hero of this story. She came up with the idea of hot towers, she hypothesized they were important to the circulation of the atmosphere in general. I see some friends in the audience, thanks for coming. And then, years later, she chaperoned the construction of the TRMM satellite, which ended up confirming that her hypotheses were correct. She also mentored scientists such as myself, and so she's the hero. So here's the TRMM satellite, it's been in space since 1997, and I work in the group that processes data there, and we sit on this huge pile of data and when time permits we're allowed to figure out, you know, the patterns and mysteries that are hidden in it. Bolted to the bottom of the satellite, you can see kind of a large yellow rectangle, it's the size of a king-sized bed.
^M00:10:01 And that's a radar. Now, it's great to have it in space because its collecting observations everywhere; before the TRMM radar launched, your only shot at getting CAT scans of hurricanes was weather service radars on the ground. They have thirty foot dishes, they use a mega-Watt of power, and they can only see maybe a hundred or two hundred miles over to the ocean. So if you want to collect statistics of hurricanes, where they form and where they live, you need a radar on a satellite. And I'm going to stop here to explain why the radar is so amazing, because it's better than science fiction. Since it's a radar, it's got pulses of energy. And it's running off solar panels. So it's not going to send a mega-watt of power; it actually sends only one watt of power. That's the amount of energy that an ordinary flashlight with two batteries is transmitting. Now it concentrates that energy in little pulses, one millionth of a second long, and it sends a thousand of them every second down towards the cloud. Now, the cloud droplets themselves don't react with that radiation, but raindrops and ice chunks that are big enough to fall, they absorb a tiny bit of it. And the rest of the radiation continues, and then the layer lower down absorbs a tiny bit. And then they re-emit that in every direction. So radar basically makes a cloud glow, very faintly. And a tiny bit of that glow comes back miraculously right at the satellite. It's ten to the negative fourteen Watts of power are intercepted by the satellite for every one of these little pulses. So, the radar can't just measure that tiny amount of energy, but it can measure gradations, which is the difference between torrential rain and light rain. So that's amazing, but it gets better than that, because the radar knows exactly how long it took for that energy at the speed of light to get to the cloud, re-emit, and come back. And the speed of light is 'pokey' compared with this technology, the satellite can transmit three pulses of energy: it takes about three thousandths of a second for that first pulse to come back, and the satellite measures exactly when it came back, and so it can tell exactly how far away the cloud was from it and it knows exactly where it is so it can tell you not only how strong it's raining there but how high off the earth's surface it is. And height matters in the atmosphere, so that's the amazing technology. Here's an example. This is what the TRMM radar saw in hurricane Sandy last year, 2012, one day before it hit New Jersey. To orient yourself, find the eye in the middle. There's an eye wall around there; it doesn't exactly look like a donut. It looks like a donut with a bite cut out of it, but nonetheless that's what a hurricane looks like when the machinery is working, when it's sucking the energy out of the ocean's surface and transforming it into the kinetic energy of winds. There's no hot tower here, but nonetheless I wanted to show you this is what the, we stripped away the clouds, we're looking at the rain regions. This is areas where up-drafts have lifted rain drops and ice chunks and energy's being transformed there and the reason why this was interesting was because there was debate in the forecast community and it made it out to the weather channel about whether or not Sandy was still a hurricane at this point and it wasn't clear. So here comes a TRMM satellite, 3D CAT scan, and the hurricane machinery was working. Now at the same time there was a weather front bringing a second source of energy into the system, so it was a very complicated and messy system, but TRMM shows you the hurricane machinery was working. I will attempt to advance to the next slide. There we go. So this, a month earlier, is hurricane Isaac hours before it hit Louisiana. The eye is the dark thing in the center. There is an eye wall circling around it and you see this is actually a very delicate looking hot tower, but this is a hot tower. We can tell because it reached high enough up that the up-drafts were lifting precipitation above the troposphere and into the stratosphere. There's this- height matters. And I'm going to pause to tell you why height should matter. So, in the troposphere, the layer that normally confines the weather, it's top is about as high as commercial aircraft fly. So, when you're flying to California, you're at 35,000 feet, you're at the tropo-poz, the boundary layer. When air gets above that, it's no longer buoyant and rising like a hot air balloon, it's pushed back down. It's negatively buoyant and so the higher clouds can penetrate into the stratosphere, you know more energy's being released and it had more of a head start. So, that's why height matters. Now, incidentally, in this case, the hurricane was intensifying and the forecasters didn't know it. At the time of this observation, the forecasters thought this hurricane's sliding into Louisiana at a steady intensity. However, in the post-season analysis, the weather service goes back and collects all the observations that they didn't have in real time and so the tropical storm report said no, actually it was intensifying almost to the very moment of landfall and just before this tower formed, the intensification had continued. So here's a tantalizing coincidence. Here's a hot tower, we know extra energy is being released because it's overshooting the troposphere, but is there a pattern? So, we have to look at statistics. Now, Joann Simpson saw some of these early results and was kind enough to say I should keep working on counting hot towers in hurricanes and walked me two doors down from her office and introduced me to Jeff Halbiston [assumed spelling] at NASA and he was another of her protegees and he and I collaborated on this result. This was published a few years ago and so, this is real science. We have stacked plots. The top plot is for the population of hurricanes where the TRMM satellite did see a hot tower in the eye wall. So, there's a lot of energy released. And you'll notice, there's a lot of red for the top plot. Red is for intensification. The little red number tells you 67% of hurricanes with hot towers we found they were intensifying. Now we drop to the bottom of those three plots. That's the other extreme slice of hurricane population. These towers had very shallow eye walls. They're like the hurricane Sandy picture I showed you. Very modest eye wall and only 14% are intensifying. So with this single observational quantity that you can measure in a single instant with radar data, you've got a clue about whether or not a hurricane's intensifying. So, the next step was, by the time we had published this, Jeff Halbiston was already working on another problem, also partially at Joann Simpson's encouragement, that a single hot tower has so little energy in it, that how could it possibly affect the whole hurricane. A hot tower is maybe 3 miles across and the hurricane is hundreds of miles across. The hot tower lasts an hour, the hurricane would last for a month if it didn't hit land and one did recently actually. So, Jeff said what you really need to look at is convective bursts. And convective bursts is a scientific jargon term for a sequence of hot towers that form on one side of the eye wall. It was an interesting thing that happens, that NASA scientists and others at Universities have really fleshed out only in the last ten years, and that's that hurricanes aren't a uniform ring, the donut analogy isn't perfect. There's actually many hurricanes inside the hurricane. They're called meso-vortices, they're spinning things that spin around inside the main vortex and they are like little nests that allow hot towers to shoot up inside them. So you get these meso-vortices spinning around the eye wall and every time they hit a favorable region a hot tower shoots up.
So for a day you can have almost a continuous sequence of hot towers. Now that's ejecting enough energy. It's reasonable to suppose that energy could cause the intensification. It's not just some random coincidence about the hot towers. So with the TRMM satellite you can look at convective bursts. It's the only radar in space and it only flies over any given hurricane once every few days. So I turn to the national weather service. The radar is available for free. The decade archive goes back years and if you have a question you can look through it to get the answer. So, as I mentioned some of these are on the coast and they can see a couple hundred miles over the ocean. Now, they don't have the beautiful 3 dimensional resolution of the TRMM radar. There's only a few scans you can get, but it's just enough information to look for convective bursts because you get an observation every five minutes. Continuous observations. So, here's the chart of results that I got from the ground radar observations of convective bursts. I've been leaving out some of the details of how this research is actually done. You get a pile of data and you have to choose how to analyze it. If what you care about is hurricane intensification, you want to get a radar-based definition of convective bursts that is the most powerful definition for finding out which hurricanes intensify and which ones don't. So we found that, what's frequent hot towers? We found that if there was a hot tower at least one third of the time over a period of time at least 6 hours long, then here's how good that definition is, using no other information about the hurricane, this is how good it is at identifying periods of intensification.
^M00:20:13 We only had 18 cases because hurricanes don't conveniently hover near the US coast long enough to do this kind of analysis so this is what we get. 31% of the time there was a lot of hot towers, of convective bursts, and the hurricane intensified. That's red for danger. The green number is 52% of the time. The hurricane didn't intensify and there were either no hot towers or they were very infrequent and so we wouldn't call that a convective burst. These results seem like not very good because they're low numbers but if you add 31 and 52, that's close to 100% of the cases were correctly identified using this radar-based definition. And another way to look at the results are take what you can see. You can see a convective burst, so under the yes column, you see that 31 versus 7, you see that it's about 4 times more likely that it's intensifying the knot if you see a burst. Then you switch to the no column. You see that if there is no convective burst then five times as many of them aren't intensifying as are. So these are actually pretty good results. However, I hope I won't offend any statisticians in the room, but this is only statistics. It doesn't prove why this is happening. In fact, it doesn't tell you anything about why. Statistics are a prelude to science. They invite you to come up with an explanation that changes how you think about what you're studying, so now we'll try to do that. So, hurricanes are an engine. They have a well-defined set of parts constrained to work together in a certain way. That's backwards. Moving forwards. So, if we're going to look for physical mechanisms, let's pause for a second and think, what exactly is a hot tower, physically? It's empty air. 99% of it is just gas and mixed in with that gas, about 1/10 of 1% of the mass of a hot tower, if you take a cubic yard of it, is rain drops and ice chunks. This is a picture of a real rain drop. Usually they're small enough to be spherical. When they get big they become hamburger bun shaped just like some NASA logos. These are pictures of ice that actually fell out of a cloud and this brings up an important point. I need to come clean on this. Hot towers are icy cold. No, stay with me. Even at the equator, if you go about three miles up, the air is freezing cold and any rain that's falling has frozen or it's just ice chunks that have formed. Of course this melts before reaches the surface although in hurricane Sandy they did dump a couple feet, I think in West Virginia, of snow but usually you think of rain in hurricanes. But where a lot of the energy transformations happen it's icy cold. So why are they called hot towers? They're called hot because objects this large will not stay lifted up in the air unless a strong up-draft was rising faster than they were falling through the air. So, how do you get an up-draft? You get an up-draft because when water freezes or condenses, it releases energy which warms that air slightly warmer than its surroundings and so the air floats up. So, the reason my hot towers are hot is in honor of the energy that makes them rise so high and that can lift ice chunks above the troposphere. So, now for hot towers in hurricanes. We're going to try to get a mechanism that explains how this works. So, hurricanes are fueled by the ocean that's warmed by the sun and the way you get heat out of the ocean is by evaporating sea water. Now, the faster the wind blows under the hurricane, the more water you get. There's a feedback loop and that's something you can understand because if you're hot and you're sweating you want a fan blowing on you cause that accelerates the evaporation which sucks more heat out. That heat can't be destroyed, energy is conserved. So when that water condenses, it releases a heat back into the air. So that's what hot towers are doing. They form directly over the eye wall. The eye wall is a place where the winds are fastest underneath. They have these little meso-vortices that provide nests for them to form particularly high and so more energy is released in them than in the rest of the eye wall. You have evidence of that because you see them go high, but that's the case. Now, you've got the heat, turned into kinetic energy with strong up draft. Now you've got air moving. Mass can't be destroyed either, so normally the top of the eye wall has air flowing out at the top. The anvil spreads out in every direction away from the hurricane. But with a hot tower suddenly pumping all this air in, it has to go somewhere and some of that air pushes onto the eye. In fact, pushes down on the eye. And by the ideal gas law, if you compress air you heat it. If you pump up a tire, you're going to heat it up. So, you're heating that central cloud-free eye of the hurricane. Now, the difference between a tire and a hurricane is that the eye wall doesn't have a rigid boundary, so some of that air can leak out as you're pushing down on it. So, the net result is not more mass in the eye, but just a warmer eye and warm air is less heavy and so at the bottom of the eye, the pressure drops. It's already low. There's a low pressure center but the pressure decreases. And, by another complicated principle called the gradient wind balance, the winds circling around the low pressure center accelerate as they try to get at that low pressure center. They're not actually intelligent, but, so they're circling around and so that is the steps. It seems very complicated but this has been a hard-fought battle to piece this together. People have flown through hurricanes with different instruments. They've released drop-sons, these metal cylinders with parachutes that fly down to the hurricane and radio back exactly temperature, pressure, and humidity to build up this machine of the hurricane. And it explains why, if you release energy in the eye wall through hot towers, for example, some of that energy will get transformed into accelerated winds, which increases evaporation which gives you more fuel for hot towers. That's why you can get these bursts where just for a day at a time there's lots of energy going into the hurricane. That's backwards now. So, to review, we have observations that suggest a hot tower in the eye wall is associated with intensification. Now, we have a physical mechanism that explains why that makes sense. You take energy from the ocean's surface through evaporation. It shoots up in the hot towers. Some of it, there's no hot tower in this picture, by the way. This, it's a picture taken by a hurricane hunter aircraft flying through the eye of hurricane Katrina in 2005 and if there were a hot tower it would be jutting up through the top of the eye wall, that bright thing in the back. And some of that air would be falling down into the eye. So, we have a mechanism. The nice thing about science is you can test your mechanisms. So, this is to review where we are. We've got our observation, we've seen a pattern and we've got a mechanism to explain it. Now we're going to do a back of the envelope calculation. On the left this is Dave Nolan, works at the University of Miami, and in science you need to borrow from other people's results. You can't get anywhere on your own. And Dave did really fun things with hurricane models, which allowed me to test the mechanism I've just presented to you that a lot of people worked out. So, what Dave Nolan did was he spun up a hurricane simulation and he just magically dropped energy. He dropped it far away from the eye wall and he saw convection form there. It brought moisture. And this is just based on a model, it's based on the laws of physics. There's none of this machinery conceptual stuff that I'm talking about. It's just the laws of physics. Energy is conserved, matter is conserved. And so he found the hurricane would weaken. And then he put the energy somewhere else and then waited for the hurricane to respond by the laws of physics. And he found that only in the eye wall that the hurricane intensified. And he gave us an efficiency factor. He said if you dump this many jewels of energy, then between 4 and 11 percent of that will end up as accelerated winds in a few hours. Now, the TRMM satellite is really good at estimating jewels of energy because we're seeing rain drops and ice chunks and for every gram of water that condenses there's an well known number of jewels of energy. So what I had to do was take the energy input that TRMM saw in a convective burst, a statistical sample of convective bursts, and multiply it by the efficiency factor that Dave got us; so then we knew how much kinetic energy there would be. And the last step was knowing how to spread that kinetic energy around the existing wind field. And that was another person's results that helped us do that. So, in the end we came up, this is how much energy convective bursts, a sequence of hot towers, can eject in the hurricane eye wall. It's 6 X 10 to the 17, if you count the zero. That's a lot of energy. That's as much energy as the United States' generating capacity in two weeks.
^M00:30:02 That's how much the hot tower releases in twelve hours. And multiply that by the efficiency, and we found that it was possible to increase the hurricane's intensity by a full category on the just five categories of the Saffir-Simpson scale. So that qualified as rapid intensification, it's a big change, it's something to worry about. So we've found a pattern in the observations, we've proposed a physical mechanism, we tested it with a back of the envelop calculation, and we saw that this mechanism could account for a significant change in intensity, not just some small, non-measurable quantity. So, what do we still not know? As a scientist, hopefully I've given you a way of thinking about hurricanes as a machine that converts energy from one form to another. What we'd like is for next year's hurricane forecast to be better. That's a problem for forecasters. At best, scientists can provide food for thought for the people; there are people that know, thinking how can I make next year's forecast better, what project should I work on? And they might look at results like this, or there are other teams of researchers trying to find other ways to use observations of the intensity of convection to predict wind. And they might try something out based on that. I mean with science you never know who's going to use the results, or whose results you're going to need. It's kind of fun, you find something, you put it out there. In my personal opinion, I think there's another way these results can be used, because when I'm looking at a hurricane that's bearing down on New Jersey, or DC, or New York City, anywhere where I have people that I, you know, that are family members, I want to pit my mind against the hurricane, trying to guess what it's going to do. And when you're listening to forecasts, different people will say, well it might do this, it might do that, and there are simple things that you can just look at the hurricane, and they give you clues. Hot towers aren't the only one. And so it gives me food for thought, and I think you could maybe become better informed consumers of weather forecasts if you learn some of these little tell-tale signs. And it's not just you that's putting your mind against the storm. At the national hurricane center in Miami, there are dozens, there are dozens of different ways of predicting intensity, and there's a single human being on duty at any given time who has to make a decision, which model do I believe. And that person can sometimes go outside the envelope of what the computer models are saying, or there are simple observational tricks that'll say, this [inaudible] suggests danger for rapid intensification. And so, all this converges on this one person who has to decide what the official forecast is, and once they decide, it's disseminated through all these different channels. And so results like this are also food for thought for the forecaster on the midnight shift, trying to decide if there's going to be rapid intensification right before landfall. So that's, we'd still like to know how best to incorporate this conceptual understanding in better forecasts. But there's different ways that might happen. But there's also observational questions that I would like to answer so I can move my little corner of the research world forward, and fortunately, next year on Valentine's Day, it's scheduled that the next best thing will launch. This is the global precipitation measurement mission, the GPM mission, and this is, it was built at NASA Goddard, the radar instrument was built by the Japanese, and it's integrated here at Goddard, the guys with the funny shower caps on are watching it being lowered last year into a thermal vacuum test chamber at Goddard, and I labeled the instruments. What's really great for my research, I mean, it's going to help a lot of people. But for me, what's exciting is that it has a duel frequency radar. You can see the king sized bed, which is a KU frequency radar, and in the back you can see a KA, that's about the size of a baby's crib. That high frequency radar, when used in tandem with the frequency we're used to, used together, it'll help us tackle something called the drop-sized distribution. In order to understand hot towers, and how strong the updrafts are, we need to know if it's just a few big chunks of ice, or a lot of tiny chunks of ice. With a single frequency TRMM results that I've shown you, we have to guess at what the drop site, this is like true confessions, we have to guess, we're not sure; it's educated guesses, but with GPM, we'll actually know. And only strong updrafts can lift large chunks, so by knowing the drop size distribution, we'll know updrafts, which will be helpful actually for modelers who are wondering how strong should these updrafts be up here; it's very hard to measure updrafts. And the other thing we don't know is illustrated in this picture. This is a picture of a hurricane simulation, and it looks messy. And that's because in reality hurricanes are messy. There's lots of things happening on many scales all at the same time. And when I look at this picture, I think this doesn't look like an engine, this doesn't look like a well-defined set of parts interacting in a well-defined way, however, this is because we've left out some of the messy details. It's still, the hurricane ancient analogy is still a powerful way of describing patterns that we see in observations, and it can lead us to incite. However, it doesn't describe everything, and I put this picture up, this is my last slide, because I want to let you know, there's a lot left to do, and the back stages of science conferences and hurricane conferences, people talk about the limits of predictability, and they worry that some of this complexity that we don't have yet in our models, or that are in our models but we can't understand how it's working, they make it impossible to predict a convective burst in a day, because if a small variation might trigger a burst, but that small oscillation isn't captured in the inputs that you're feeding into your model, you might totally miss it. So, and this occasionally makes its way into the scientific literature, but there's complexity we don't yet understand. And before I talk about things I don't understand, I'll stop here, so thank you very much.
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[Applause]
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>> Thank you very much. I know that we have all learned a lot today. Mostly I now know how hot towers aren't cold, but, the contradiction in that I'm sure that we have many questions though arising from the presentation and we'd like to entertain them at this time. So please.
>> Can you repeat the question.
>> Dr. Owen Kelley: Right. I'll repeat the question. They said your voice will be used on the recording, but they can't actually hear you, they can only hear me, so you're anonymous. Go ahead. Dr. Bell, by the way, this is Dr. Bell, he's the reason why I'm here. He, I have to tell this story. I was going to apply to graduate school. He was a professor at my college, St. John's College in Annapolis, Maryland, and I told him two days before Christmas vacation senior year, I'm not going to apply, and he said give me one good reason, and I said, well they won't accept me, I'm a liberal arts major, why would they let me, you know, enter the sciences for graduate school, and he said that's not a good reason. And so I applied, and you know, I worked really hard, and so here I am, so he gets the right to ask a question. Yes?
>> The question [inaudible] TRMM satellite, will NASA maintain it as well in operation [inaudible]. Will it maintain [inaudible]?
>> Dr. Owen Kelley: Yes, and the question was, thank you, repeating the question, Dr. Bell wanted to know if the TRMM satellite will be maintained by NASA, even though the new instrument's going up, I won't go back to that slide, the GPM satellite. And the answer is yes, NASA will. And in fact, for further scientists it's absolutely wonderful if you can get an overlap between old and new, because then you don't have a fifteen year data set from TRMM, and then some other data set, you have a continuous record of hurricane hot towers, and other sort of things. And it is, it takes effort and money to keep things going, and in fact there was talk of shutting down the TRMM satellite after it had done its official three year mission. I mean, we're on the fifteenth year of a three year mission right now, which is pretty good, and the instruments are working, and we have fuel enough to continue for a while longer before the sun heats up the atmosphere, and the next solar max probably drives us down. But there was actually an outcry among the operational community, the Navy, the Air Force, other countries said don't take the TRMM satellite down, it's helping us protect our assets. And so sometimes TRMM seems like just a research satellite, but no, sometimes it's in the front line and in fact the naval research lab, which Dr. Bell is also affiliated with, has a website up where they take every satellite up there that can give you information about hurricanes, and they make pictures in real time. And for agencies in countries, third world countries, that can't afford to have an agency like NASA, this naval research lab website gives them a snapshot of exactly what's going on in the hurricanes, so the answer is yes, we'll keep it going for you. Other questions? They can be hard or easy, they don't have to, yes.
>> I'm just curious, in your research, your observations, do you notice whether hot towers forming in one quadrant of a hurricane are more likely, [inaudible] each quadrant,
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versus the southwest, or does that not really have any impact.
>> Dr. Owen Kelley: That's an area of research. And people have done simulations to try and tease that out, and people have done observational studies. The question is, do you see one preferred quadrant of the hurricane; I mean a hurricane is often divided into quadrants based on its direction of motion. There's the front left quadrant, well, there's the front right quadrant where the forward motion of the hurricane, I'm trying to not get it backwards, the forward motion of the hurricane combines with a circular motion, so the winds are actually faster on that side. So that's one preferred location for intense convection because if the winds are blowing faster over the ocean on that side of the hurricane, you're getting extra evaporation, so you're getting more fuel, because a hurricane is an engine that transforms energy from one form to another. Another possible preferred direction is based on wind shear. So wind shear is when the winds at one altitude blow in a different direction, or faster, than the winds lower down. And when there's wind shear, on the down shear side, there's a favorable region for the outflow to be pulled out faster. And so that'll help a hot tower form because then the exhaust fumes have somewhere to go. And usually there's some complex interaction between the forward motion of the storm giving a favorable direction, and the wind shear giving a favorable quadrant. So yeah, there's, and that's an interesting area of research if you're an atmospheric dynamicist and you just worry about the equations of motion, that's like a fun project to work on. So, yes in the back.
>> Yes, I wonder if you would comment on your experiences spending four years in a liberal arts school, moving into [inaudible].
>> Dr. Owen Kelley: Yeah, yeah sure.
>> [Inaudible], what was that like?
>> Dr. Owen Kelley: OK, so the question is, I guess I spilled the beans by telling you where I came from originally. The question is, if I, what was it like to go from a liberal arts student into a graduate school in physics, and was there a disconnect? Well, St. John's college is a very interesting place, we spend four years sitting around a table, and we work our way through the classics: we start with Plato and read the Bible sophomore year, and the enlightenment junior year, and the federalist papers, and all these wonderful things, and we don't really take tests. I mean, we're, you have to participate or you get kicked out. So you go from there to graduate school, and, actually, Dr. Bell gave me some coaching on how to make that possible, he's helped a number of people make that transition. The trick for me was getting really good at undergraduate math, learning differential equations and stuff like that. I didn't have any of the undergraduate physics class, I mean, I'd read Maxwell's equations, the original paper but that's not the same thing as an undergraduate background. So when I hit graduate school, I had to promise them, 'hey give me a chance, give me a year provisionally, and if I can pull this off, then admit me as a student.' And the transition wasn't, it was very scary, but I think life is scary. I think graduating from college is a scary time, and it turned out I had an advantage that I wasn't afraid to ask questions, and I would confront the professor during a lecture and after the lecture, and I think the professors liked it, because it showed someone was paying attention. The other students wanted me to hush up, but no, so I think you have to be willing to fight for what you want, and if that's understanding physics, then you go to the professor and say, hey, I don't get this, what am I missing, and what do I need to do? Sometimes they say you need to read the book five times until you get it, you know, and you do that before you come back. No, so it was a frightening and wonderful experience and I think it was good for me so. Yes?
>> Simple question on your slide with Hurricane Sandy.
>> Dr. Owen Kelley: Sure.
>> So there were no hot towers in it?
>> Dr. Owen Kelley: Right.
>> It was very devastating.
>> Dr. Owen Kelley: Yes.
>> Were there hot towers in other areas of it?
>> Dr. Owen Kelley: There actually were far outside the hurricane. There was frontal energy impinging on it from every direction, but those weren't enough to make it more devastating. No, I can tell you my personal answer for it. I think Hurricane Sandy was so bad, and I kept thinking, forecasters should say this. This would give the people a sense of what's about to hit. Hurricane Sandy, by the way the Saffir-Simpson scale, how are we doing on time, do I need one, OK. So the Saffir-Simpson scale, the Simpson in that is the husband of Joann Simpson, so it's Bob Simpson who's in that scale. That scale originally had a wind speed associated with it, like the scale is now, but also a pressure, because generally hurricanes are a certain size. And so a certain low pressure would be associated with a certain wind speed. Sandy had a category four, low pressure center. It was a very low pressure, the winds weren't that strong. It also is very huge. So there's a basic scientific principle that says the winds are proportional to how quickly the pressure is falling as you're going towards the center. So a little tiny storm doesn't have to have a very low pressure, and the sides of that pressure curve can be steep, and you get a strong wind. Hurricane Charlie in 2004 was like that. He was a tiny little eyeball, had category four winds. Now let's go to Sandy, with the question was, why was Sandy so devastating? It wasn't because of hot towers somewhere else, it was because we had a category four pressure drop, spread out over thousands of miles, so it wasn't going to miss New York City, it wasn't going to miss east coast, it was going to hit everybody. The winds at any one location were only category one winds, because the slope of that pressure as it moved towards the eye wasn't that steep, and so that was, that was why, partially why it was so bad. But the other reason why, I'm sort of, NASA does science and NOVA does forecasts, so I'm sort of like dangerously sliding in the wrong direction. But the other reason why Sandy was so dangerous was because it did that weird left hook. It went up parallel to the coast, so it got plenty of moisture over the ocean, it didn't sort of slide against North Carolina and stuff like that. The functioning engine of the hurricane stayed clear over the ocean, and it suddenly dodge into New York City, and that sudden dodge into New York City directed the surge, so it was a very high surge. So you had bad surge, you had this huge wind field that you weren't going to get lucky and have it miss you, so that's why hurricane, those are two reasons I can think of why hurricane was bad. If you call the National Hurricane Center, I bet they could tell you more reasons, exactly what happened, so. Yeah, in the front?
>> You were talking about the hot towers as if they're there or they're not. But I was wondering are there hot towers that are there for temporarily that you see it before and after, not there?
>> Dr. Owen Kelley: Yeah. That's right.
>> Is that an issue? And are the analytics good enough to determine that period, or you just have to get the data right [inaudible].
>> Dr. Owen Kelley: Sure, so the questions is 'I talk about the hot towers being there or not, but what if one just happened right before the satellite flew over, how do you fit that into your theory?' That's a very good question, and that's something I wrestled with a few years ago. And it turned out I was saved. If hot towers had started to form randomly, then yeah. If you're going to observe the hurricane for just one minute, for two days, and then come back two days later, how could you possibly know if there's lots of hot towers, or if you just missed one? The later research that used the ground radar showed you that if one forms, generally a lot of them form. If the conditions are good enough for updrafts in a hurricane to shoot out of the troposphere, then there's probably going to be a sequence of them. That frequently happens. It doesn't always happen. So I was actually really lucky with my first results, where I combine independent observations of hurricanes, a single observation, a single snapshot, and when I saw a hot tower, I saw intensification. I mean, Jeff Hoverson was warning me about this. He says, what you're probably seeing is just one blip in a convective burst, and some of those cases where the hurricane intensified and you did see a hot tower, there might have been a convective burst there, and you were just had just had super bad luck that time. So, and that's the problem with science. Especially the kind of science that I do, observational science. You can never see what you actually want to see. What I would like to see is a three dimensional wind field, and rain field in a hurricane constantly, you know. But nothing can do that for you, and that's part of what makes it exciting. You've got to make do with what you've got. And it turns out, like I say, the TRMM observation is surprisingly good, because if one hot tower forms, you're likely to have a bunch of them, and you need a bunch of them to, you know, turn the fate of a hurricane, perhaps [inaudible] was a scientist, so she was giving me the tough questions. Go ahead.
>> Are you incorporating global warming theories into this to see the changes maybe?
>> Dr. Owen Kelley: Right, I mean, there are people who are doing that. The question is 'are you incorporating global warming theories into your hurricane research?' I personally am not. There are people who are both looking at global warming, and there are people looking at something called Paleo-tempestology, which is going back to the last ice age and seeing the record of storms, and trying to see variations on those time scales.
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Honestly, the work I do is on the scale of hours, you see a tower, and on a scale of hours, that energy's going to work through. For the climate questions, you'd want to ask a climatologist, because there's different sets of things you have to be careful about when you're thinking about climate, that I don't have to worry about if I'm just looking at now and the next few hours. So I don't know, I wish I knew the answer to that, but I don't know what climate change is going to do to hot towers and hurricanes. Yes?
>> Following up on that question, if you have fifteen years of data, and ocean temperature has been warming, right, and as well as air in the atmosphere, have you noticed in different hurricanes more hot towers forming in the last fifteen years?
>> Dr. Owen Kelley: The question is 'have you seen a signal, you've got fifteen years of data, that should be long enough to pull something out, the ocean has warmed during that time, so come on, come clean, tell us if there's a climate change signal there.' So the easy answer is I have not looked for one, and so I clearly haven't seen one. However, I think we should be cautious in hoping for a signal in fifteen years, because the year to year variation of ocean in the regions, because hurricanes form in one place, they don't form over the globally averaged ocean surface temperature. Obviously, in 2005 we had a ton of hurricanes, we ran out of letters, we went up to hurricane Ziga, we went to the Greek alphabet, which is useful, because I'd gone to St. John's and I'd learned ancient Greek. But no, seriously, so is there a signal? The year to year fluctuations are larger than the fifteen year change in global average ocean surface temperature. Worse than that, in a given season, the warm pool of ocean can move around, and there's questions of, I mean, to get a hurricane going, just like a hot tower needs kind of a nest, these meso-vortices that spin around in the eye walls so that it has protective place to grow, but hurricane needs a nest to grow. And that's a little wave coming off Africa. A lot of the strong hurricanes come off Africa. So you never know if the warm pool that maybe is a standard deviation above the climalogical average, but maybe that doesn't line up this month with the waves coming off of Africa, and so it doesn't help you. And so there's so many complicating factors, I haven't tried finding the pattern, but I think it would take some effort to see that. I mean, there have been plenty of scientists who have come on the record and say, hey, hurricanes are going to get this much worse by 2100, or only a couple percent worse, or something like that, but those are the talks I go to, and I listen as an audience member, I can't say I know of a trend, so, yes? In the front.
>> Are you also looking at tropical cyclones and stuff like that?
>> Dr. Owen Kelley: Right. Right, so I had to simplify some things in this talk. I talked about hurricanes all the time, but the same class of storm is called a typhoon when it hits in Japan, and it's called just a plain cyclone in Australia, they're all tropical cyclones, it's a general scientific term. So with a TRMM satellite, that's the great thing about it. It's an unbiased sample around all of the tropics, and so yeah, we're looking at typhoons too. Typhoons, you know, hurricanes that form in the west pacific, heavy advantage that there's a large run where they don't hit any big land forms, and so they have a longer chance to have a hot tower form, and a convective burst form, and has a chance to run its course, instead forming and then smacking land instantly, and then you never know whether the energy had percolated through. And so we've looked at the pacific. The scary thing about the pacific is they don't have routine aircraft observations, and aircraft radars can do [inaudible] and collect radar in situ over a period of time, and so we have to go with the satellite data. So there's questions about how different, are typhoons really the same animal as hurricanes? So my sample size wasn't really large enough to do a good categorization of individual ocean basins, so I pulled them all together. So, yeah but they definitely form there and they're dangerous. In fact, the worst hurricane/typhoon in terms of human life hit Bangladesh, in I think 1970, and I think half a million people died. I mean, so hurricanes are a terrible thing everywhere.
>> And I hate to end on that note, but I think we want to thank Dr. Owen Kelley for being with us today, and if you have any further questions, we could perhaps bring them outside to the lobby where there is some handouts that NASA has kindly brought. And we also have some of the works by Dr. Simpson, and some other items from our collections about hurricane prediction. Thank you very much for coming.
>> Dr. Owen Kelley: Thank you.
>> This has been a presentation of the Library of Congress. Visit us, at loc.gov
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